1. Field of the Invention
The present invention relates generally to shoulder fired firearms and particularly concerns cartridge gas actuated semi-automatic and full automatic firearms that have a bolt carrier mechanism, with a bolt member located therein for linear movement during firing activity. More particularly, the present invention also concerns a gas key that is mounted to the bolt carrier by retainer screws and defines an internal gas supply passage that is in communication with a gas supply port of the bolt carrier. More specifically, the present invention concerns means for preventing any leakage of cartridge gas at the gas key/bolt carrier planar surface interface.
2. Description of the Prior Art
Virtually all semi-automatic and full automatic tactical rifles, such as the military version AR16, which has semi-automatic and automatic settings and its semi-automatic equivalent, the AR15, have a bolt carrier within the receiver of the firearm. The bolt carrier defines a bolt chamber within which a rear portion of a bolt member is positioned. The bolt member is provided with gas seal rings which establish movable sealing with an internal seal surface of the bolt chamber. The bolt carrier member is linearly moveable within the upper receiver of the firearm mechanism by cartridge gas pressure acting on the gas seal rings of the bolt member when the firearm is discharged and cartridge gas is conducted from the gas port of the barrel of the firearm, through a gas tube and through a gas supply passage of a gas key member and into the bolt chamber. The bolt carrier member defines a wall structure having a gas supply port and defines a generally planar gas key mounting surface that is intersected by the gas supply port.
A gas key, also having a generally planar surface is secured to the planar surface by retainer screws and defines a gas supply passage that is in communication with the gas supply port. When the gas key is properly positioned and seated on the generally planar gas key mounting surface, the planar surfaces of the gas key and bolt carrier member will be tightly secured in face-to-face engagement by the force of the gas key retainer screws. This retained relationship of the gas key member and the bolt carrier member defines a planar surface interface which, in the past has been considered to establish a sealed condition that prevents cartridge gas leakage. However, since the cartridge gas pressure that is conducted from the cartridge gas supply passage of the gas key, through the gas port of the bolt carrier and into the bolt passage of the bolt carrier is quite high, some gas leakage frequently occurs at this planar surface interface.
Any gas pressure leakage at this interface, tends to deplete or decrease the gas pressure that enters the bolt chamber of the bolt carrier and thus decreases the cartridge gas actuating pressure that acts on the seal area of the bolt member and is applied through the bolt member to the bolt carrier member. The cartridge gas pressure is employed to move the bolt carrier member within the upper receiver, against the force of a buffer and buffer spring assembly that is present within the gun stock mechanism. When gas leakage occurs at the planar surface interface, the cartridge gas pressure entering the bolt chamber is diminished or decreased to some extent. This decreased gas pressure can result in insufficient gas actuated movement and force of the bolt member, resulting in ineffective extraction of a cartridge case after a cartridge has been fired and perhaps causing jamming of the cartridge extraction and feeding mechanism of the firearm. Moreover, as usage of this type of firearm continues, the amount of cartridge gas leakage at the gas key/bolt carrier interface can change and cause the cycling operation of the firearm extraction and charging mechanism to change, and thus interfere with proper cycling of the firearm mechanism during use. Therefore, it is desirable to provide an effective seal at the gas key/bolt carrier interface to provide positive assurance that no cartridge gas will leak under any condition of firearm usage.
It is also desirable to provide a sealing mechanism at gas key/bolt carrier interface which will not be adversely affected by excessive heat or cold. This feature is particularly important during sustained use of a semi-automatic or automatic firearm for rapid fire for long periods of time or during use of the firearm when the ambient conditions are extremely cold.
To overcome the gas leakage that typically occurs at the interface of the gas key with the bolt carrier, it is desirable to develop a seal that establishes a bridge at the planar surface interface, establishes positive sealing with the gas key member and with the bolt carrier member and prevents cartridge gas from leaking between the engaged facing planar surfaces.